Abstract
Dipeptides and tripeptides containing D-phenylalanine have been synthesized and compared as growth inhibitors with optically isomeric peptides containing L-phenylalanine. The amino-acids in these peptides were arranged in the same sequence as in gramicidin S. Limited antibiotic activity was observed with synthetic peptides, but no difference in activity was found between a tripeptide containing D-phenylalanine and bne containing L-phenylalanine. The significance of these results in relation to the origin of antibiotic activity in peptides is discussed.